An online (在线) video has become popular these days. In this video, a Chinese police officer pretends (假装) to be blind (眼盲的). She tries to get on a bus with a guide dog (导盲犬). But the driver refuses (拒绝) her. The dog looks very sad. If you were on the bus, would you let them get on? Guide dogs help blind people every day. How much do you know about them?